I is for...

I is for Isotope analysis

And now for the sciency bit! All the elements found in the Periodic Table – such as hydrogen and oxygen – are made of atoms. Every normal atom is made up of a specific number of protons, electrons and neutrons. Isotopes are atoms of the same element with a different number of neutrons, which means they have slightly different weights.

Isotope analysis uses the oxygen isotopes in human teeth to work out where people come from. It works because nearly all of the oxygen that goes into building bones and teeth comes from the water that was drunk during childhood (water is made up of the elements hydrogen and oxygen). The water that we drink comes from rainfall, and the type of oxygen isotopes in rainfall depends on the local natural environment. Water in warm climates has more heavy isotopes (so-called ‘oxygen 18’) whereas water from cold climates has more light isotopes (‘oxygen 16’).

Oxygen isotope analysis of the teeth from skeleton of the Bronze Age “Amesbury Archer” found more oxygen 16 isotopes. Archaeologists were therefore able to work out that he came from somewhere with a colder climate than we find in Britain today, possibly central Europe!